Electrical permutation lock



May 4, 1954 H. c. MILLER ELECTRICAL PERMUTATION LOCK 3 Sheets-Sheet 1 Filed Sept. 5, 1950 e in u rw K WQ m o m m INVENTOR HazzyMZ/er ATTORNEYS BY M May 4, 1954 H. c. MILLER ELECTRICAL PERMUTATION LOCK 3 Sheets-Sheet 3 Filed Sept. 5, 1950 INVENTOR Hmyfi. Mlle! ATTORNEYS Patented May 4, 1954 UNITED STATES PATENT OFFICE 2,677,814 ELECTRICAL PERMUTATION LOCK Harry G. Miller, Fairfax, Va. Application September 5, 1950, Serial No. 183,167

2 Claims.

The present invention relates in general to permutation locks, commonly referred to as combination locks, and is particularly directed to a permutation lock in which a plurality of electrical relays are operated sequentially to close a final circuit which operates the bolt of the lock.

Permutation locks, commonly referred to as combination locks, are, of course, well known. The majority of these locks in the past have been of the mechanical type, in which a plurality of mechanical elements, usually referred to as tumblers, each having a notch or gate, must be brought into predetermined alignment to receive a fence before the bolt can be withdrawn. The

security of such locks is dependent upon the fact that the number of orders or permutations of the possible relative positions of each of these tumblers before all of the gates are brought into proper register to permit the operation of the lock, is so large that the chances of a person not familiar with the combination being able to align the gates and open the lock, is so small as to be negligible. In these previous locks the tumblers are usually operated directly by a manually controlled dial. However, devices are known in which the tumblers or their mechanical equivalents are operated by remote control through appropriate electrical circuits.

These prior art mechanical combination locks, however, have been found to be fairly susceptible to being worked by skilled safe-crackers. Because of the mechanical elements involved in such locks, a faint click may be detected when one of the tumblers is rotated into proper aligned relation to receive the fence. Therefore, by working the dial through repeated trials, as the combinations are comparatively few, the dial readings for the aligned positions of the tumblers may be worked out by detecting these mechanical clicks to break the combination.

The present invention relates to a permutation lock in which the mechanical elements which might give rise to mechanical clicks or noises suggestive of the combination have been eliminated, and in which permutations are obtained by utilizing a plurality of electrical relays which must be operated in a particular sequence in order to energize the final bolt actuating circuit. Such an electrical system provides a marked improvement in the security of the look, as the tumbler clicks above referred to are eliminated. Additionally, electrically controlled elements are provided to energize a remote alarm device, if

the manual actuated selector elements, such as pushbuttons and the like, not part of the lock combination or in improper sequence, are depressed or manually actuated, and to deenergize the entire system of relays if the proper combination oi] pushbuttons are not actuated within a preselected time interval. An arrangement is also provided intercoupling the sequentially arranged relays with the pushbutton panel for rapidly and simply selecting and changing the combination. Means are also associated in the instant device for operating the look from a distance so that the safe may be in one part of a room or building and the controls may be in another part of a building or room which is constantly under the surveillance of a guard or watchman.

An object, therefore, of the present invention is the provision of a novel electrical permutation lock, which readily lends itself to separation of the locking elements from the electrical circuits, and which provides further security in looks for safes and the like.

Another object of the present invention is the provision of a novel electrical permutation lock wherein the permutations for actuating the bolt are obtained by actuating a system of electrical devices, to eliminate mechanical noises from which the combination might be broken.

Another object of the present invention is the provision of a novel electrical permutation lock wherein a plurality of electrical devices must be operated in a particular sequence in order to eiiect withdrawal of the bolt.

Another object of the present invention is the provision of a novel electrical permutation lock wherein a plurality of manually operable elements controlling a selective system of electrical devices must be operated in proper sequence within a preselected time interval to efiect retraction of the bolt.

Another object-of the present invention is the provision of a novel electrical permutation lock having a plurality of manually actuated switches, less than the whole number of which must be actuated in a preselected sequence to efiect re- P traction of the bolt, and wherein actuation of switches other than those forming the combination, or actuation of the combination-forming switches in improper sequence, will energize a remote alarm.

Another object of the present invention is the provision of a novel electrical permutation lock having time-limitation means for resetting the system on failure to manually set up the combination within a preselected time interval and having remote alarm means energized when error is made in attempting to manually set up the combination.

Other objects, advantages and capabilities of the present invention will become apparent from the following detail description taken in conjunction with the accompanying drawings, wherein only a preferred embodiment is shown:

In the drawings:

Figure l is a perspective view illustrating the physical assemblage of the components of the permutation electrical lock embodying the present invention, showing the manner in which the components are assembled in their respective housings;

Figure 2 is a rear elevation of the mounting panel supporting the combination selector terminal board, viewed from within the electrical unit housing;

Figure 3 is a vertical section of the conibina" tion selector grid supporting panel, taken along the lines 3-3 of Figure 2;

Figure i is an elevation of the locking block assembly and bolt latch mechanism, with parts broken away to illustrate the interaction thereof Figure 5 is a horizontal transverse section of the locking block and associated operating means therefor, taken along the lines of Figure l;

Figure 6 is a vertical transverse section of the intercoupling between the locking block and solenoid core, taken along the lines E--Ei of Figure 4;

Figure '7 is a vertical transverse section or a safe door, taken along the lines l--l of Figure 4, illustrating a preferred manner of mounting the locking assembly housing and pushbutton housing thereon; and

Figure 8 is a schematic circuit diagram of the electrical circuit of the instant electrical permutation lock.

Referring to the drawing, wherein corresponding parts are designated by like reference charcters throughout the several figures, particular reference being had to Figure 3 showing a schematic diagram of the electrical circuit, a panel of manually actuated switches or pushbuttons, generally indicated at H3, is provided. The number of these pushbuttons in the pushbutton panel ill will preferably exceed the number or" digits forming the loci: combination by a relatively large number of buttons, in order to increase the security and reduce the likelihood of a lockbrealrer being able to break the combination. For purposes of these detailed descriptions, only 10 of such pushbuttons are illustrated, these being numbered successivel lilo through W9. A common lead Ii connects one element of each of the pushbuttons lilo to lily, through a lead 12 to the negative side of a battery or other suitable source of direct current voltage, schematically indicated at it.

The other elements of each of these pushbutton contacts we to lily are each connected to a gridlike unit forming a combination selector termi nal board, generally indicated at I l, This combination selector terminal board comprises a plurality of mutually parallel, vertically arranged, elongated conductor elements or busses indicated at i511 to 57. A plurality of mutually parallel generally horizontally arranged elongated conductors it to 22, inclusive, are likewise provided, extending in a plane parallel and closely adjacent to the plane of the vertical busses lea to Q57, each of the horizontal conductors 16 to 22 extending across the entire series of vertical bosses Ilia to I59. The desired combination may be selected by bridging the points of intersection of the vertical busses a to I57 and the horizontal conductors iii to 22, by suitable conductive elements such as those indicated generally at 23, this being operative to set up the combination by the selection of these various bridging points as will be more fully described hereinafter.

Actuation or the lock to release the safe door is eilected by ,means of a plurality of electrical relays, which are intercoupled in a relay system so that the relays must be progressively energized in a preselected sequence, the last relay in the sequence having contact means for actuating the locking bolt. These relays are schematically indicated at 24 to 29 inclusive, the first five of which are provided with two groups of contact elements. The contacts E la to 28a form an electrical interlock for looking the relay coil associated therewith in circuit once the coil is energized, and contacts 2 th to 280 form a conditioning relay in the sequence system to condition the next succeeding relay coil in the sequence to be energized.

Referring to the sequence system of relays more specifically, the horizontal conductor IS in the combination selector grid I4 is coupled directly to the top of the coil of relay 24, and to the movable contact arm of the relay contact grou The fixed contact element 24a of the relay contact element 240. is intercoupled by means of a lead 53B with the fixed contacts of each of the relay contact groups 25a, 26a, 21a, 28a, and intercoupled by means of a lead 3| with. the negative side of the D. C. voltage source The lower side of the relay coil 24 is intercoupled by means of a lead Sea with the lower side of each of the other relay 00115 25 to 29 inclusive, which lead is indirectly coupled to the positive side of the D. C. potential source [3 in a manner to be later described.

The movable arm of the other relay contact group 2451) is coupled directly to the horizontal conductor 11 in the combination selector termi nal board 14, and is adapted to be drawn into contact with contact 25b on energization of relay coil 24, the contact 24b being coupled directly to the top of the next succeeding relay coil to condition relay 25 to be the next energized. Thus on energization of the relay coil 24 by depressing pushbutton Illa, it being assumed that the vertical. bus 15a coupled thereto is bridged to the lowermost horizontal conductor is by bridging conductor 23, the contact group i l-c coupled thereto will be closed, locking in the circuit through relay coil 26, and the movable arm of the contact group 2M) will contact the point 2% to condition the second relay 25 to be energized on depressing the button lflb. The pushbutton iflb, as illustrated in the drawing, is intercoupied to the horizontal conductor ll of the combination selector grid M, by bridging the bus llib thereto.

The relay 25 is likewise provided with two contact groups, the contact group 25a forming electrical interlock. to lock the coil 25 in currentconducting relation through the leads 3 and 3| to the negative side of the D. C. voltage source IS. The movable arm of the other contact group 25b is coupled directly to the horizontal conductor l8 of the combination selector grid l4, and is adapted, on energization of the coil 25, to close the circuit throu h the contact point 25b coupled to the top of the next succeeding relay coil 25 to condition the same to be energized on depressing the selector button associated with the vertical bus in the selector grid |4 bridged to the horizontal conductor 8.

Likewise, the next succeeding relay coils 26, 21 and 28, are provided with contact groups 25a, 21a and 28a, the movable arm of which is coupled to the top of its associated coil to close the circuit through the leads 3i! and 3| to the D. C. source l3 and lock the respective coils 26, 21 and 2B in energized condition once current has been passed through them. Each of these coils 2B, 21 and 28 likewise have contact groups 28b, 21b and 28b, the movable arms of which are coupled directly to the horizontal conductor elements i9, 211 and 2|, respectively, in the combination selector terminal board. 011 closing the contacts 26b, 27b and 28b by energization of the preceding relay coil, the relays 21, 28 and 29, respectively, are conditioned to be energized by depressing the pushbut-tons in the pushbutton panel |0 associated with the vertical busses bridged to the conductors l9, 2|! and 2|. To this end, the movable arms of each of the contacts 26b, 21b and 28b are adapted, when their associated relay coils are energized, to move into electrical contact with fixed contact points 2%, 21b and 282), respectively, coupled to the top to the next succeeding relay in the sequence series.

The relay 29, the last in the series of relays forming the relay sequence system, is provided with but one group of contact elements, indi cated at 29a, having a fixed contact point 29a coup-led directly through leads 32 and 33 to the positive side of the D. C. voltage source I3. The

movable arm of the contact group 29a is coupled through a lead 34 to the coil of a solenoid 35, the solenoid 35 having a plunger 35 intercoupled by means of a lug 31 with the inclined slot 38 of a movable locking block 39 forming the retractable latch elements of the lock. The other side of the solenoid coil 35 is coupled through a lead 40 to the common lead 30, which in turn is connected to the negative side of the D. C. source |3 through lead 3 i, so that energizing the relay coil 29 closes the contact group 29a and passes current through the solenoid coil 35 to retract the locking block 39.

An additional relay, indicated at 4|, forming an error alarm relay, is likewise provided, this relay having two groups of contact elements 4| a and 4|b. The group of contact elements 4m forms an electrical interlock for the relay coil 4|, in the same manner as electrical interlock contacts 24a to 26a, and to this end is provided with a movable arm coupled to the top of the relay coil 4|, and a fixed contact element 41a coupled to the lead 30, and thus to the negative side of the D. C. voltage source |3 through loads 30 and 3|. The group of contact elements 4|b constitutes the circuit means normally applying B+ voltage to the lower common lead 30a for the coils 24 to 29 inclusive, and to this end com prises a movable arm coupled directly to the lead 32, and through leads 32 and 33 to the positive side of the D. C. voltage source l3. The movable arm of the contact elements 4|b is nor mally in closed contact relation with the fixed contact 4|b', which contact is coupled through lead 42 and through normally closed bimetallic contact 43 to the common lead Ma coupled to c the lower end of each of the relay coils 24 to 29. In this manner, when no current is flowing through the relay coil 4| and the movable arm .of the group of contact elements MI) is in closed conductive relation with the fixed contact Mb,

B+ voltage is applied from the source l3 through leads 33 and 32, movable arm of the contact group 4| b, fixed contact 4122', leads 42 and bimetallic contact 43 to the common lead a at the lower end of the relay coils 24 to 29. A resistor 44 is disposed across the relay coil 24 parallel therewith, and in proximate heat exchange relation with the bimetallic con-tact elements 43, to open the contacts 43 when current has flowed through the coil 24 and resistor 44 for a preselected time interval, the resistor 44 radiating heat sufiicient to separate the bimetallic contact 43. This preselected interval is normally set at 15 seconds. It will be apparent, therefore, that due to the radiation of heat from the resistor 44 to the bimetallic elements 43 on energizing coil 24, the entire sequence system of coils must be energized within the preselected time interval in order to energize the solenoid and withdraw the locking block 39, else the circuit will be broken from the lower side of the coils 24 to 29 to the positive side of the D. C. voltage source |3 by opening of the bimetallic contacts 43.

The top side of the relay coil 4| is coupled through lead 45 to the uppermost horizontal conductor element 22 of the combination selector grid Hi, this element being bridged by means of conductive elements 23 to each of the vertical busses which are not bridged to the horizontal conductors I6 to 2| and thus forming part of the combination. It will be apparent, therefore, that actuation of any of the pushbuttons, lilo to lily inclusive, in the illustrated circuit, will momentarily close the circuit through the lead 45 and relay coil 4|, to energize the error alarm relay and break the circuit between the positive side of the voltage source I 3 and the common conductor 300. at the lower end of the relay coils 24 to 29, thus deenergizing each of these coils.

Energization of the error alarm relay coil 4| likewise moves the movable arm of contact group 4|b into circuit closing relation with a normally open fixed contact 4H2", which is directly intercoupled through lead 48 with an audible alarm device or buzzer 41, which in turn'is coupled through the leads 3!! and 3| to the negative side of the voltage source I3. Closing of the movable arm of contact element 4th with the contact 4|b" will close the circuit through the alarm or buzzer 41, preferably located remote from the safe on which the instant lock is mounted, to produce an audible signal indicating that an error has been made in attempting to set up the combination on the pushbutton panel ID.

A suitable bimetallic thermal contact 48 is disposed between the lower end of the coil 4| and the lead 33, the bimetallic contact being disposed adjacent a thermal resistor 49 disposed close to the coil 4| and parallel therewith to open-circuit the error alarm relay coil 4| after energization thereof for a preselected time interval, preferably five minutes.

An additional series of fixed contacts 24b to 2%" are provided in normally closed relation to the contact arms 24?) to 2331), respectively, and coupled through a common lead Ell to the lead 45. It will be apparent that depression of any of the buttons H112 to I81 before the prior relays in sequence series are energized, will energize the alarm relay 4| in the same manner as depression of the buttons leg to lily to indicate error.

Assuming that the combination is set up on the combination selector grid |4 in the manner illustrated in Figure 8, that is, with the sequence system relay coils 24 to 29, inclusive, coupled to the pushbuttons Illa to I01 respectively, by bridging the vertical busses I connected thereto to the horizontal conductors Hi to 2| respectively, operation of the electrical circuit actuating the locking block solenoid is substantially as follows:

On depression of the pushbutton Illa, the negative side of the D. C. potential source i3 is coupled through the lead l2 and horizontal conductor IE, to the top of the first relay coil 24, the bottom side of the coil being coupled through normally closed thermal contact 43, lead 42, fixed contact Mb and movable contact arm Mb, and leads 32 and 33, to the positive side of the voltage source l3. Energizing the relay coil 24 in this manner draws the movable arm 24a in the closed circuit relation with the fixed contact 24a, coupled through the lead 3| to the negative side of the D. C. source l3, to lock the relay coil 24 in energized condition. The movable arm of the contact group 24b is likewise drawn into circuit closed relation with the fixed contacts 2%, thus closing the circuit between the horizontal conductor 1'! on the selector terminal board It and the top of the second relay coil 25. Depression of the pushbutton Nib in like manner established the circuit through the horizontal conductor ii, the movable arm 24b, and fixed contact point 24b to the top of the relay coil 25, thus coupling the negative side of the D. C. source [3 to the top of the relay coil 25. Since the lower end of the relay coil 25 is coupled through conductor 32c, normally closed thermal contacts 43, lead 42, fixed contact 4112 and movable contact arm Mb, and leads $2 and 33, to the positive side of D. C. source 13, a closed current path is thereby established through relay coil 25, thus energizing this coil, locking the same in energized condition by closing the contact group 25a, and conditioning the next relay coil 28 to energized by closing the circuit between movable contact arm 25b and fixed contact point 251). In like manner depression of push-buttons lllc and Hid in proper succession energizes the relay coils 26, 21 and 28, looking the same in energized condition by closing the group of contacts 26a, Zia and 28a, and conditioning the next successive coils to be energized by coupling the top of the same to the next successive pushbuttons in the series. Energizing of the last pushbutton In) in the combination, applies B- to the top of the relay coil 29, energizing the same and closing the contacts 29a and 29a to energize the solenoid 35, and withdraw the locking block 39 from looking position. If the entire combination of pushbuttons Ilia to ifif inclusive are not depressed in the proper sequence and within the preselected time interval required for the thermal contacts 43 to open due to heat evolved from current flow in the resistor 44, the entire system will be reset, as the circuit between the lower ends of the relay coils 24 to 29 inclusive and the positive side of the voltage source l3 are opened by the thermal contacts 43.

Depression of one of the pushbuttons iii in im proper sequence will energize the error relay coil 4 l, to energize the remote alarm 4 For example, assuming that the pushbutton [0a has already been depressed and the operator erroneously depresses the button lilc next, the movable contact 261) will be in its normally circuit closing relation with the fixed contact point 2511', which is connected through the lead 5!! and lead 45 to the top of the error alarm relay coil M, the coil. 25 not having been previously energized, so that the energizing circuit will be established through the coil 4! to move the contact arm 4!?) and energize the remote alarm 41. In like manner, depression or any of the pushbuttons lllg to I07 inclusive, bridged to the uppermost horizontal conductor 22, will establish the circuit through the alarm relay coil 4| to energize the alarm 41. After the error alarm relay coil 4| has been energized, it is locked in by the interlock contacts Ha, Ha, to continuously energize the remote alarm 41 until the bimetallic contacts 48 are opened from heat evolved due to conduction of current through the resistor is for the preselected time interval.

The circuit components above described, and the mechanical locking elements, readily adapt themselves to a physical assemblage having the improved security characteristics aforementioned. The electrical components are ideally suited to be arranged into separate units for the pushbutton panel Hi, the selector terminal board l4 and associated relays, and the remote alarm unit. These are preferably arranged as illustrated in Figure 1, showing an exploded view of the assembly, and Figure '7, showing the units mounted on a safe door.

The pushbutton panel In is disposed in a pushbutton housing 60, arranged on the front of a safe door, indicated at 6| in Figure 7, or the pushbutton housing ESO may be disposed at a position remote from the safe if desired. The housing 60 is preferably provided with a pivoted cover 62 covering the panel mounting the buttons Illa to its, and. a suitable lock 63 may be provided on the cover to maintain the housing cover 62 locked and further discourage unauthorized access to the pushbuttons.

This pushbutton housing Bil is interconnected with a bolt actuator assembly housing 65 by means oi a multi-conduit lead 66 and a multitap plug 61 adapted to be connected to a suitable multi-tap socket, not shown, on top of the actuator assembly housing 65. The actuator assembly housing is adapted to be mounted on the safe door ti on the inwardly disposed surface thereof, to prevent access to the housing 65, and houses all of the relays 24 to 29 and 4|, the bimetallic time delay contact elements 43 and 48, and the bolt actuating solenoid 35.

The actuator assembly housing 65 is provided with a unique arrangement for changing the combination of the electrical lock, that is, chan ing the interrelation between the sequence series of relays 24 to 29, and the pushbuttons Illa to lay. This means comprises a rectangular insulating panel 68, forming a cover panel for the actuator assembly housing 65. The panel 68 is preferably formed of a suitable insulating plastic, and carries on the inwardly disposed face thereof the vertical busses or conductors [5a to [5 of the combination selector terminal board i4. These vertical busses 15a to I59 are secured at their upper and lower ends to the insulating panel 68 by means of suitable rivets 69, the lowermost series of rivets 69 forming terminals to which the leads intercoupling the vertical busses l5a to I5 to the pushbuttons Ilia to Illa are soldered or otherwise secured. The busses 15a to I5 are each provided with a series of spaced threaded openings IS, in registry with corresponding openings 68' in the insulating panel 58. These are arranged in transverse horizontal rows, in alignment with a plurality of horizontal conductors or busses IE to 22 likewise secured at their ends to the insulating panel 68 by suitable rivets, and disposed on the opposite face of the panel 68 from the busses l5a to I57.

The horizontal conductors are coupled to the 9 various relays 24 to 29 and 4|, and are each provided with rows of threaded apertures 10 in registry with the apertures 68 and IS in the panel 68 and busses l5a to I57.

The combination desired can, therefore, be set up on the selector terminal board by bridging the horizontal busses I6 to 22 to the vertical busses I 50. to I57 through the apertures 68 in the panel 68, by means of threaded screws constituting the bridging elements 23. It will be apparent that the combination may be changed around to any desired sequence relationship between the relays and the pushbutton panel H) by withdrawing the screws 23 from the threaded openings in the horizontal and vertical busses, and changing their relative positions to bridge .difierent groups of busses. f v

The locking block actuating solenoid 35 is mounted in the upper right hand corner of the housing 65, as illustrated in Figure 4, and is interconnected to the locking block 39 by means of a lug 31 formed in the armature 36 of the solenoid 35 and extending through an inclined slot 38 in the block 39. As more clearly illustrated in Figures 5 and 6, the solenoid arm 36 is provided with a bifurcated portion at the lower end thereof forming arms 36' adapted to embrace the locking block 39 along opposite sides thereof. A guide block H is mounted on the rear of the housing 65, and is provided with a vertically extending concave recess, indicated at 12, to accommodate and aid in defining the movement of the solenoid armature 36, and is provided with apertured forwardly extending flange portions 13, 13, forming a horizontal guide track for the locking block 39. Suitable aperture 14 is formed in the side wall of the housing 65 to permit the locking block 39 to project therefrom.

Cooperating with the locking block is a latch plate 15 mounted on the door 6|, on a shaft 16 extending from a manual latch lever 11. The latch plate 15 is provided with a projection 15 to which a bolt I8 is pivotally intercoupled, the bolt riding in a suitable recess provided in the door 6| to guide its movement. The bolt 18 projects from the edge of the door Bl to lock the same when the latch plate 15 is in furthermost counter-clockwise position as viewed in Figure 4. The latch plate 15 is provided with a projection 19 formed with a perpendicular flange 80 at the end thereof adapted to overlie the side of the housing 65 from which the locking block 39 projects, the flange 80 being provided with a rectangular opening 8| extending therethrough adapted to receive the end of the locking block 39 and prevent rotation of the latch lever 11 to withdraw the bolt 18 from looking position when the solenoid 35 is deenergized. A suitable curved flange portion 8| is provided on the flange 80 adapted to abut the outer end of the locking block 39 when the same has been withdrawn to allow the latch plate 15 to be rotated in a clockwise direction as illustrated in Figure 4. This flange portion BI is adapted to maintain the locking block 39 forced into inwardmost position in the housing 65 to prevent locking the latch plate 15 and bolt 18 when the lock has been released and the safe door open.

From the above description it will be apparent that a novel electrical permutation lock assembly has been devised, which eliminates all mechanical noises which might facilitate a safecracker breaking the combination of the lock, which is ideally suited to separation of the lock actuating components and the manual pushbutton components of the lock, which is provided with time delay means for limiting the time interval during which one can operate the pushbuttons in proper sequence to eifect unlocking of the lock, and which is provided with remote alarm means which will be energized if pushbuttons not a part of the combination are actuated, or pushbuttons a part of the combination are actuated in improper sequence, to indicate that an error has been made in attempting to set up the combination.

While but one particular embodiment of the invention has been specifically shown and described, it is distinctly understood that the invention is not limited thereto, but that various modifications may be made without departing from the spirit and scope thereof, and it is desired, therefore, that only such limitations shall be placed thereon as are imposed by the prior art and are set forth in the appended claims.

What is claimed is:

1. In a combination-operated electrical lock of the type having a number of manual switches greater than the digits in the combination and elongated conductive bars arranged in spaced parallel planes closely adjacent each other with ing and disposed at the other set, each the axis of one set overlyright angles to the axis of of the bars of said one set with said relays, removable means for conductively bridging the conductive bars of each set at selected points of crossing of the bars of the two sets for establishing the combination of said lock, an additional elongated conductive bar underlying each of the bars of said one set, and

same when any with are actuated.

2. In a combination operated electrical lock of the type having a number of manual switches greater than the digits of the combination couplied to one terminal of a current source and a each other with the axes of the strips of said second series being disposed at right angles to the axes of the strips of said first series and each of the strips of said second series underlying all of the strips of said first series, each of the strips of each series having aligned apertures at their points of crossing with other strips, conductive bridging members to be removably inserted through the aligned strip apertures at selected points of crossing to electrically bridge strips of 1 each series and establish the combination oi: the lock, an additional elongated conductive strip underlying each of the strips of said first series and adapted to be electrically coupled with said alarm means, said additional strip and said strips of said first series having aligned apertures at their respective points of crossing, and conductive bridging members to be inserted through the aligned apertures of said additional strip and each of the strips of said first series uncoupled with the strips of said second series.

References Cited in the file of this patent UNITED STATES PATENTS Number Number Name Date Nelson Jan. '1, 1919 Harmer Nov. 19, 1929 Leschke et al. Apr. 25, 1933 Chase Aug. 22, 193B Ballentine Oct. 12,1937 Haselton Dec. 6, 1938 James Apr. 23, 1940 Joel, Jr. Mar. 2, T948 FOREIGN PATENTS Country Date Germany Oct. 17, 1914 France Apr. 14, 1922 

